1. Field of the Invention
The present invention relates to optical/electrical path integrated networks, and relates specifically to a technique for notifying about information relating to traffic quantity between sub-networks, and a technique for dynamically establishing and releasing optical paths according to the traffic quantity between sub-networks.
This application is based on patent application No. 2002-045092 and No. 2002-054247 filed in Japan, the contents of which are incorporated herein by reference.
2. Description of the Related Art
Research and development is proceeding in the field of optical/electrical path integrated networks, as a technology for building high capacity networks. In an optical/electrical path integrated network, the transmission/reception endpoints are connected by optical paths. An electrical sub-network comprising a node which performs routing based on packet header information is connected to each of the transmission/reception endpoints. A first conventional example of an optical/electrical path integrated network is shown in FIG. 6.
The optical/electrical path integrated network comprises a photonic core network C and electrical sub-networks S1 to S4. The electrical sub-networks S1 to S4 must be connected by optical paths for communication to occur.
The photonic core network C comprises photonic border nodes and a photonic core node. The electrical sub-networks S1 to S4 comprise electrical border nodes and electrical core nodes. The electrical core nodes and the photonic core node are contiguous at the boundary of the electrical sub-networks S1 to S4 and the photonic core network C, and are interconnected by optical fiber links.
Optical paths are established over the photonic core network C, so as to interconnect the electrical border nodes provided in the different electrical sub-networks S1 to S4. Information is transferred transparently between the electrical border nodes over the optical paths.
When four optical paths are established as in FIG. 6, the view of the electrical sub-networks S1 to S4 is as shown in FIG. 7. FIG. 7 shows a view of a network topology comprising nodes which are capable of performing packet processing, in which the topology of the photonic core network C is hidden. FIG. 8 is a combined view of the electrical sub-networks S1 to S4 and the photonic core network C.
The electrical sub-networks must be interconnected. However, it is not necessary for all of the electrical sub-networks to be directly connected to each other by optical paths, and multiple hop routing may be used.
FIG. 9 shows an example of the connection of the four electrical sub-networks S1 to S4 in FIG. 6. The electrical sub-network S1 is connected to the electrical sub-networks S2 and S3 by a direct optical path, the electrical sub-network S2 is connected to the electrical sub-networks S1 and S4, the electrical sub-network S3 is connected to the electrical sub-networks S1 and S4, and the electrical sub-network S4 is connected to the electrical sub-networks S2 and S3, each by direct optical paths.
To transmit a packet from the electrical sub-network S1 to the electrical sub-network S4, the packet can travel from the electrical sub-network S1 to the electrical sub-network S4 via the electrical sub-network S2, or from the electrical sub-network S1 to the electrical sub-network S4 via the electrical sub-network S3, by multi-hop routing. In the same manner as FIG. 9, FIG. 10 shows an example of the connection of the four electrical sub-networks S1 to S4 in FIG. 6. Diagonal optical paths are established between the electrical sub-networks S1 and S4, and between the electrical sub-networks S2 and S3.
In both FIG. 9 and FIG. 10, the electrical border router of each electrical sub-network S1 to S4 has two electrical packet transmission/reception ports connected to the photonic core network C. How the two electrical packet transmission/reception ports provided in each of the electrical border routers should be directly connected by optical paths is determined by the traffic quantity between the electrical sub-networks S1 to S4. FIG. 9 is favorable when the traffic quantity over the diagonal paths is small, and conversely FIG. 10 is favorable when such traffic is high.
If the optical paths are established without taking the traffic quantity into consideration, then for example electrical sub-networks which exchange a high quantity of traffic may not be directly connected by an optical path, making it necessary to transfer packets by multi-hop routing, which causes a problem of congestion of the optical paths.
Furthermore, an optical/electrical path integrated network is shown in FIG. 23 as a second conventional example. This optical/electrical path integrated network is constructed from the photonic core network C and the electrical sub-networks S1 to S4. The optical/electrical path integrated network in FIG. 23 is a multi-layer network, in which optical paths are established over the photonic core network C. In this manner, the group of electrical sub-networks S1 to S4, connected by optical paths, constitutes the entire electrical network.
The photonic core network C comprises photonic border nodes 1A to 6A and a photonic core node 7A. The electrical sub-networks S1 to S4 comprise electrical border nodes 11A, 12A, 21A, 22A, 30A, 32A and 40A, and electrical core nodes 10A, 20A, 31A, 41A and 42A. The electrical border nodes 11A, 12A, 21A, 22A, 30A, 32A, 40A and the photonic border nodes 1A to 6A are contiguous at the boundary between the electrical sub-networks S1 to S4 and the photonic core network C, and are interconnected by optical fiber links. The optical paths are established over the photonic core network C, to interconnect the electrical border nodes 11A, 12A, 21A, 22A, 30A, 32A, 40A in the different electrical sub-networks S1 to S4. Information is transmitted between the electrical border nodes 11A, 12A, 21A, 22A, 30A, 32A and 40A transparently over the optical paths.
The topology of the electrical network can be virtually changed, depending on which of the electrical sub-networks S1 to S4 are connected. FIG. 24 shows how two different electrical network topologies can be realized when a single optical path network topology is applied. Furthermore, FIG. 24 describes the hierarchy of the optical paths and the electrical paths. In FIG. 24, O-LSP (Optical-Label Switched Path) indicates an optical path, and E-LSP (Electric-Label Switched Path) indicates an electrical path.
The E-LSP is routed over the electrical network, comprising the electrical sub-networks S1 to S4 which are interconnected by O-LSPS. In the connection mode #1 on the right side of FIG. 24, the E-LSP is connected by multi-hop routing. In other words, two electrical sub-networks are connected via two O-LSPs. On the other hand, in the connection mode #2 on the left side of FIG. 24, the E-LSP is connected by a single hop. In other words, two electrical sub-networks are connected via a single O-LSP.
In the terminology of graph theory, the entire electrical network must be “connected”. In other words, the electrical sub-networks S1 to S4 must be interconnected by O-LSPs. However, it is not necessary for every one of the electrical sub-networks S1 to S4 to be connected to every other by an O-LSP, and multi-hop routing may also be used. FIG. 25 shows a connected electrical network and an unconnected electrical network. In the connected electrical network, all four of the electrical sub-networks S1 to S4 can communicate via O-LSPs, but in the unconnected electrical network only three of the electrical sub-networks are connected by O-LSPs, and one of the electrical sub-networks cannot communicate with the other three electrical sub-networks via an O-LSP.
FIG. 16 shows an example in which the four electrical sub-networks S1 to S4 in FIG. 25 are connected. The electrical sub-network S1 is connected to the electrical sub-networks S2 and S3 by direct optical paths, the electrical sub-network S2 is connected to the electrical sub-networks S1 and S4, the electrical sub-network S3 is connected to the electrical sub-networks S1 and S4, and the electrical sub-network S4 is connected to the electrical sub-networks S2 and S3, each by direct optical paths. In order to transmit a packet from the electrical sub-network S1 to the electrical sub-network S4, the packet can be transferred from the electrical sub-network S1 to the electrical sub-network S4 via the electrical sub-network S2, or from the electrical sub-network S1 to the electrical sub-network S4 via the electrical sub-network S3, by multi-hop routing.
In the same manner as FIG. 16, FIG. 17 shows an example in which the four electrical sub-networks S1 to S4 in FIG. 25 are connected. Diagonal optical paths are established between the electrical sub-networks S1 and S4, and between the electrical sub-networks S2 and S3.
In FIG. 16 and FIG. 17, the electrical border nodes 11A, 12A, 21A, 22A, 30A, 32A and 40A in the electrical sub-networks S1 to S4 have two electrical packet transmission/reception ports connected to the photonic core network C. How the two electrical packet transmission/reception ports provided in the respective electrical border nodes 11A, 12A, 21A, 22A, 30A, 32A and 40A should be directly connected by optical paths is determined by the traffic quantity between the electrical sub-networks S1 to S4. FIG. 16 is favorable when the traffic quantity over the diagonal paths is small, and conversely FIG. 17 is favorable when such traffic is high.
In the same manner as the first conventional example, if in this second conventional example the optical paths are established without taking the traffic quantity into consideration, then for example electrical sub-networks which exchange a high quantity of traffic may not be directly connected by an optical path, making it necessary to transfer packets by multi-hop routing, which causes a problem of congestion of the optical paths.
Traffic quantity varies temporally, and as such even once the optical paths are established, it can be necessary to dynamically reconfigure the optical paths according to the conditions. Requiring a network administrator to manually reconfigure the optical paths in this manner according to variations in traffic increases the amount of work required for maintenance, which is undesirable.